Multiple path coherer



.INVENTOR. EDWARD A. OUADE B FREDER/C. WOOD ATTORNEYS MULTIPLE PATH COHERER Edward A. Quade and Frederick B. Wood, San Jose, Calif., assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Application October 28, 1955, Serial No. 543,375

2 Claims. (Cl. 338-1) The present invention relates to coherers, and pertains more particularly to a multiple-path coherer in which the probability of tiring when subjected to a voltage of normal firing potential is much greater than is the case with a usual single path coherer.

In many electrical and electronic mechanisms, it is desirable to employ a coherer, which normally consists of a quantity of metallic powder between a pair of electrodes, usually pointed, and in contact with both electrodes. Subjecting the coherer to a predetermined minimum Voltage across the electrodes fires the coherer, or, in other words, causes a train of the powder particles to fuse together and thus provide an electrically conductive path from one electrode to the other through the otherwise non-conductive powder mass. This fused, conductive path remains intact until the powder mass is agitated, which breaks up the fused chain of powder particles and restores the coherer to its original non-conductive condition.

Coherers having numerous potential uses in electronic calculating mechanisms, but since they occasionally fail to lire, their field of usefulness in the past has not been nearly as great as it would have been if the certainty of firing could have been substantially increased.

One desirable held of application for coherers, except for their occasional failure to fire, resides in a usual matrix of an electronic calculator, wherein a plurality of wires extending in one direction are run, at least schematically, across a second plurality of wires to form a grid. For impressing information bits on such a grid it is desirable to set up conductive paths therein, so that later a reading current may be used kto test which of these conductive paths have been established, and thereby divulge information bits thus impressed thereon.

ln the past, attempts have been made to increase the firing probability of coherers, for example by employing coherers having larger r better electrodes, and by providing a plurality of similar coherers in parallel. However, such arrangements apparently have no effect on the firing probability of the coherer, since when one path, however weak or unsatisfactory it may be, is established through the coherer, current flowing along this path reduces below tiring potential the voltage impressed across other possible firing paths in the coherer.

The present invention contemplates the provision of a coherer having a plurality of probable firing paths, each of such said paths having substantially equal probability of firing, and frequently firing through a plurality of such paths when a normal firing voltage is impressed across the coherer.

The invention also provides a coherer in which a plurality of probable tiring paths in multiple are separated from each other by predetermined resistances, so that a firing voltage impressed across the coherer has a probability of firing along a plurality of such paths, and wherein the probability of tiring through any of said paths exists even after one of the potential paths has fired.

aired States Patent C 2,899,657 Patented Aug. l1, 1959 ice Another object of the invention is to provide an improved, multiple path coherer.

These and other objects and advantages of the invention will be apparent from the following description and the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of a multiple path coherer embodying the present invention.

Fig. 2 is a diagrammatic view of a fragment of a matrix of a type used for storing information bits transmitted, for example, by means of a punched card of a well known type.

Fig. 3 is a transverse sectional view through a multiple path coherer embodying the present invention.

Fig. 4 is a schematic view through the coherer shown in Fig. 3, three tired paths through the coherer being indicated by the three darkened circles therein.

Referring to the drawings in detail, Fig. l shows a group A of three similar coherers 10, 11 and 12 having similar resistors 13, 14 and 15, respectively, connected in series therewith. These three similar coherer-resistor units 16 are connected in parallel between a pair of electrode conductors 17 and 18 which in turn may be connected across a source of voltage potential V normally sufficient to fire the coherer-resistor units 16, and to maintain a firing potential across the remaining coherers after a tirst coherer of the group has fired. Since these values will vary along with other factors well known to those familiar with the art, and may easily be calculated for any known set of conditions, it will be unnecessary to set them forth in greater detail herein.

In Fig. 2 is shown diagrammatically a portion of a matrix B for use with punched card type mechanisms. As illustrated in Fig. 2, a first plurality of conductor wires 23 extends transversely in parallel, spaced-apart relation, and a second plurality of conductor wires 24 extends uprightly in similar parallel, spaced-apart relation. The rst wires 23 are electrically separated from the second wires 24, with the exception that a multiple path coherer 25 of the type illustrated in Fig. l is connected across each crossing point of the first wires 23 with the second wires 24.

The upright second Wires 24 are indicated as being capable of being selectively grounded, while the first wires 23 are indicated as being capable of being selectively connected to a potential of V, which is the desired firing Apotential for the coherer at any intersection when impressed across the two wires crossing at that intersection. Since the switching mechanism for connecting the firing voltage to a selected wire of each of the first and second plurality thereof is well known, and since it forms no part of the present invention, it will not be illustrated or described in detail herein.

Assuming that the upright conductor 24 is grounded, and that the transverse conductor 23 is connected to a voltage source of firing potential, or V, the coherer 2S' tires along one or more of its probable tiring paths. Coherers at other intersections in the grid B may be similarly tired as required.

The firing voltage of V is used for establishing an information pattern on the grid, or as it is termed, for writing For checking to determine which of the coherers have fired, or readingj a lesser voltage is used, for example V/ 5. This reading voltage is suicient to carry the reading current through the tired coherers, but not to re any unfired coherers.

A modified form of multiple path coherer C embodying the invention is shown sectionally in Fig. 3, and schematically in Fig. 4. Here a pair of electrodes 29 and 30 are mounted in parallel, spaced relation. The electrodes 29 and 3i) have outer layers 29a and 30a, respectively, of electrically conductive material and are lined on their inner faces with layers 31 and 32, respectively, of electrically lresistive material. Between the resistance layers 31 and '32, and in-contact withfboth thereof, is a quantity of metallic powder 34.

When a tiring voltage, for example V, is impressed across :the electrodes 219 and 30, plural probableiiring paths 37, 38, 39, 40, 41, 42 and-`43 through the coherer areV indicated in Fig. 4. These probable tiring paths, as will be apparentfrom-the foregoing description of Fig. l, will exist along any path through the powdersuiiiciently remote'fromany other' probable or already fired pathto have suicient'resistance therebetween to provide tiring potential acrossl the new' path. From theupper electrode 29 Van'ininite number of-paths exist through theupper resistancev material 31'to'the powder '34. These paths through the upper resistance are indicated schematically in Fig. j4 byy the upright zig-zaglines 45. The resistances transversely'b'etween thesey adjacent paths 45 in Fig. 4 are indicated by thetransverse zig-zag lines 47. Similar resistances are indicated in the lower resistance element 32 by upright zig-zag lines 49 and transverse zig-Zag lines -50.

Assume that the coherer' C has fired along a path 39 (Fig. 4) or 39 (Fig. 3). Firing potential still willbe impressed across the electrodes 29 and 30 along'pathsV remote from the fired path due tothe presence of the resistances 31 and 32 which limit the dropvin potential across the electrodes upon the tiring along each additional path through the-powder 34. Thus the coherer C is shown'as having tired along paths 37, 39`and-42 in'Fig. 4, and along paths 37 39 and 42. in Fig. 3.

Asan example of how the combination of a plurality of parallel coherer paths of the type'shown'in Figs. 1 and Zawould increase the probabilityof tiring, if Pw) is taken as the probability that a coherer 'Will'iire at v voltage, then P=1vP wris-its probability of not tiring. If P()=.99`9,'then with a single coherer, P=.001=103. With" three coherers each lhaving an equal probability of tiring, however, P=(1-P)3 or .0013 or 10"9. To achieve this result would of course require a multiple path coherer such as that shown in Figs. 1 and 2 with three separate coherer-resistor units in parallel. The form of the invention shown in Figs. 3 and 4 would have a much higher probability of tiring than a conventional single path coherer, but unless the number of its probable firing paths (n) were known, its probability of tiring 'or not tiring would be lditieult to calculate.

The invention provides a multiple path vcoherer in whichthe probability of'iring is' greatly increased over that of a conventional, single path coherer, and without requiring a substantial increase in voltage above its minifrom the scope of the invention as set forth in the appended claims.

Having thus described the invention, what we clairn as new and desire to protect by Letters Patent is defined in the following claims.

We claim:

1. A multiple path coherer for use in a circuit having substantially no other resistance therein comprising a pair of electrodes mounted in parallel, spaced apart relation, each-electrode comprising an outerplate portion of substantial sui-face area and of highly conductive material, afacing ofresistance materialI over the-inner-surface of each outer plate portion, each facing being relatively thin proportionto its width, and a quantity of sesV metallic powder interposed between, and in contact with substantially the entire inner surfaces of the resistive facings of both electrodes, the resistive facings being of a thickness, and having an insulative value, so that when a tiring current isimpresse'd acrossvthe outer plate portions, and after-the iiringofthe coherer along a irst path through the powder, the resistive facings maintain aiiring potential across the-coherer, anda plurality of other probable ring pathsthrough the powder remain, each of saidother paths being separated from such rst path and from'each other by aresistance greater than the resistance between said outer plateportions and the powder.

2. A- multiple path coherer for use in a circuit having substantially lno other resistance ytherein comprising a pair of electrodes mounted in parallel, spaced apart relation, ea'chelectrode comprising an outer plate portion of substantialsurface area andof highlyl conductive rnaterial, a facing'ofresistance material over the inner vsurface of one of the outer plate portions,4 each facing being relatively thin in relationto its'width, and a quantity ofmetallic powder interposed between, and substantially lling the entire space between the electrodes, whereby, when a tiring current is impressed across the outer plate portions, and after the tiring of the coherer along a iirst path throught-helpowder, the resistive facing maintains a tiring potential across the coherer, and a plurality of other probable tiring paths through the powderremain, each of said other` paths-being separated from such iirst path and from eachother byA a resistance greater than the resistance between the outer plate portion having the resistive facing thereon and the powder.

References Cited in the le of this patent i UNITED STATES PATENTS 254,190 Berliner Feb. 28, 1882 716,000 De Forest Dec. 12, 1902 883,241 Sargent Mar. 3l, 1908 908,504 vSargent Ian. 5, 1909 993,024 Burke May 23, 1911 1,107,255 Bradley Aug. 18, 1914 1,144,399 Turney 'Iune 29, 1915 2,660,640 Wolf Nov. 24, 1953 

